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BL 6 inch gun Mk II – VI
United Kingdom |type= Naval gun Coast defence gun |is_ranged=YES |is_bladed= |is_explosive= |is_artillery=YES |is_vehicle= |is_UK=YES |service=1880 - 19?? |used_by=Royal Navy |wars= |designer=Royal Gun Factory (RGF) |design_date= |manufacturer=RGF and EOC |production_date= |number= |unit_cost= |variants=Mks II, III, IV, VI |weight=Mk II : 81 cwt or 89 cwt (4½ tons)Mk II weighed 81 cwt as originally built; 89 cwt after chase-hooping to strengthen it and shortening by 12 inches. "Treatise on Service Ordnance 1893" pages 258-259 Mks III, IV, VI : 5 tons barrel & breechThese weights include additional weight of hoops added to strengthen the guns. Treatise on Service Ordnance 1893; Text Book of Gunnery 1902 |length= |part_length=Mk III : (25.53 calibres) Mk IV, VI : (26 calibres)Text Book of Gunnery 1902, Table 12 page 336 |width= |height= |crew= |cartridge= |caliber= |action= |rate= |velocity=Mk III, IV, VI : Mk III, IV, VI 1960 ft/sec firing a projectile using E.X.E. (gunpowder) or cordite MK I propellant size 20 or cordite MD size 16 QFC guns : QFC guns used a gunpowder or cordite Mk I charge for a muzzle velocity of . Text Book of Gunnery 1902; Treatise on Ammunition 1915. BLC guns : BLC guns used a cordite Mk I charge for a muzzle volocity of , or MD size 16 charge for a muzzle velocity of . Hogg & Thurston 1972, pages 139 & 142. |range= |max_range= Text Book of Gunnery 1902 quotes 10,000 yards for Mks III, IV, VI |feed= |sights= |breech=3 motion interrupted screw. De Bange obturation. |recoil= |carriage= |elevation= |traverse= }} The BL 6 inch guns Marks II, III, IV and VI'Mark II = Mark 2, Mark III = Mark 3, Mark IV = Mark 4, Mark VI = Mark 6. Britain used Roman numerals to denote marks (models) of ordnance until after World War II. Hence this article covers the second, third, fourth and sixth models of BL 6-inch guns in British service. were the second and subsequent generations of British 6-inch breechloading naval guns, designed by the Royal Gun Factory following the first 6-inch breechloader, the relatively unsuccessful BL 6 inch 80 pounder gun designed by Elswick Ordnance. They were originally designed to use the old gunpowder propellants. They were superseded on new warships by the QF 6 inch gun from 1891. Development history These were Royal Gun Factory designs, although they were also manufactured by Elswick Ordnance. Mark II Mk II followed the early weakly made and less powerful Mark I 80-pounder and introduced a 100-pound projectile, which became standard for British 6-inch guns until 1930. It consisted of a much thicker steel barrel with wrought-iron jackets shrunk over it and as originally introduced weighed 81 cwt (9072 pounds). The gun proved to be too weakly constructed, and 5 steel chase hoops were added to strengthen it and the gun was shorted by 12 inches to rebalance it, resulting in a bore length of 144 inches (24 calibres) and final weight of 89 cwt (9968 pounds), or 4½ tons. These guns were relegated to non-firing drill use following a burst gun incident on HMS ''Cordelia in June 1891.Treatise on Service Ordnance 1893, pages 258-259 Marks III, IV, VI Mark III finally introduced an all-steel construction, with a steel barrel and steel breech-piece and hoops shrunk over it, weighing 89 cwt (4½ tons). However, as originally introduced Mk III was still limited to weak charges and low muzzle velocity, and most guns were strengthened by being chase-hooped to allow a full powder charge of 48 lb gunpowder and muzzle velocity of 1,960 feet per second. This brought the gun weight up to 100 cwt (5 tons).Treatise on Service Ordnance, 1893 Mk IV incorporated the improvements to Mk III. Mk VI differed from Mk IV only in having slightly simplified construction. Marks III, IV and VI became the most commonly deployed versions, and their widespread adoption would indicate they were considered successful. Marks III, IV and VI were interchangeable and had the same performance. They are generally referred to as "6-in 5-ton B.L.R." in contemporaneous publications such as Brassey's Naval Annual. Guns equipped the following British warships : * s and s, laid down 1878 : Mk II * s laid down 1880 * s laid down 1881 *''Colossus''-class battleships of 1882 *''Leander''-class cruisers of 1882 *[[HMS Hotspur (1870)|HMS Hotspur]] as re-gunned in 1883 : Mk II * s laid down 1885 * laid down 1885 *[[HMS Bellerophon (1865)|HMS Bellerophon]] as re-gunned in 1885 * of 1885 *''Conqueror''-class ironclad turret ships completed 1886 - 1888 : Mk II * s laid down 1887 *[[HMS Rupert (1872)|HMS Rupert]] as re-gunned in 1887 * , launched in 1888 * s as re-gunned in the 1880s : Mk II QFC conversion From 1895 many ships' guns were converted to QF to use the same brass cartridge case and charge as the modern QF 6 inch guns. They were designated '''QFC for "QF Converted", and the new Mark designation began at I over the old gun Mark e.g. I/IV was the first version of Mk IV gun converted to QFC, II/VI was the second version of Mk VI gun converted. Coast defence gun is mounted, behind), awaiting restoration at the Bermuda Maritime Museum, in the Royal Naval Dockyard, Bermuda.]] Mk IV and VI guns were widely used in coast defence around the British Empire, both on hydro-pneumatic disappearing mountings and Vavasseur slides (inclined slides that absorbed recoil). A small number of Mk IV and VI guns had their old 3-motion breeches replaced by modern single-motion types and the chamber lengthened to accept a more powerful cartridge, and became the BLC (breech loading converted) coast defence gun in 1902. They attained a maximum range of using a 15 oz cordite cartridge. They were replaced by the modern Mk VII as they became available, and were declared obsolete in 1922.Hogg & Thurston 1972, page 139 BLC Siege gun Mk IV and VI BLC guns were also fitted out with wagons in 1902 to allow them to be transported as semi-mobile siege guns - the gun and siege platform were transported as separate loads, the siege platform was assembled at the firing site and the gun mounted on it. When World War I broke out in 1914, 2 batteries of these BLC siege guns were equipped with primitive wheeled gun carriages with traction engine wheels and sent to France as heavy field guns. They were towed by steam traction engines. They had limited recoil buffers and required chocks in front and behind the wheels when firing. These guns had a maximum range of 14,200 yards. They were soon replaced in action as guns in 1915 by the more modern 6 inch Mk VIIHogg & Thurston 1972, page 142 and were then converted into 8-inch howitzers. World War I conversion to 8 inch howitzer Britain was desperately short of heavy field artillery at the beginning of World War I, and in 1915 old BL 6-inch guns were bored out and shortened to produce BL 8 inch howitzers as follows :Hogg & Thurston 1972, page 152 *12 BLC guns Mk I/IV became 8-inch howitzer Mk I *6 BL Mk IV and VI guns became 8-inch Howitzer Mk II *6 BL MK IV and VI guns, but adapted for different carriage, became 8-inch howitzer Mk III *8 BLC Mk I/VI adapted for Mk IV carriage became 8-inch howitzer Mk IV Mk V Mk V was a longer (30-calibres, 183.5 inch bore) unrelated Elswick Ordnance export gun. Image gallery File:BL 6 inch Mk II gun diagram.jpg| Mk II gun File:BL 6 inch Mk III gun diagram.jpg| Mk III gun, as strengthened by chase-hooping, weight of 5 tons File:BL 6 inch Mk IV gun diagram.jpg| Mk IV gun File:BL 6 inch Mk VI gun diagram.jpg| Mk VI gun File:BL 6 inch Mk III Breech Mechanism Diagram.jpg| Mks III, IV and VI breech mechanism See also *List of naval guns Surviving examples *3 guns at Green Hill Fort, Thursday Island, in the Torres Strait : Mk IV Gun No 727 dated 1890; Mark VI Nos 838 & 839 dated 1892. *Mk IV gun on disappearing carriage at Lei Yue Mun Fort, Hong Kong. *Mk IV gun No. 726 dated 1890 at Princess Royal Fortress, Albany, Western Australia Notes and references Bibliography * *Text Book of Gunnery, 1887. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE *Treatise on Service Ordnance. HMSO, 1893. * Text Book of Gunnery, 1902. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE *Manual for Victorian naval forces 1887. HMVS Cerberus website *Additions to 1890 Manual for Victorian naval forces circa. 1895. HMVS Cerberus website *I.V.Hogg & L.F. Thurston, British Artillery Weapons & Ammunition 1914-1918. London: Ian Allan, 1972. * Tony DiGiulian, British 6"/26 (15.2 cm) BL Marks I to Mark VI External links *Diagram of Mk IV or VI gun on Hydropneumatic disappearing mounting Mk IV (or actually Mk I ?) at Victorian Forts and Artillery website *Diagram of Mk IV or VI gun on Barbette Mk I on Slide Mk I at Victorian Forts and Artillery website Category:Naval guns of the United Kingdom Category:152 mm artillery Category:Victorian-era weapons of the United Kingdom